Continuous casting machine reciprocation and withdrawal control system

ABSTRACT

A CONTINUOUS CASTING MACHINE HAVING A FLOW THROUGH MOLD, HYDRAULICALLY DRIVEN WITHDRAWAL ROLLERS FOR WITHDRAWING A MOLDED STRAND FROM THE MOLD, AND HYDRAULICALLY TION PARALLEL WITH OF STRAND WITHDRAWAL TO INSURE SEPARATION OF THE STRAND THEREFROM DURING WITHDRAWAL. THE WITHDRAWAL SPEED IS SELECTIVELY ADJUSTABLE TO CORRESPOND TO THE METAL POURING RATE AND CONTROL MEANS EFFECTS SIMULTANEOUS CHANGES IN THE SPEED OF THE OSCILLATING MECHANISM ACCORDING TO A PRESELECTED PROPORTIONALLY CONSTANT.

Nov. 7, 1972 1 ROKOP ETAL 3,702,154

CONTINUOUS CASTING MACHINE RECIPROCATION AND WITHDRAWAL CONTROL SYSTEM Filed Sept. 5, 1970 2 Sheets-Sheet l 3,702,154 N AND J. ROKOP ETAL CONTINUOUS CASTING MACHINE RECIPROCATIO Nov. 7, 1972 WITHDRAWAL CONTROL SYSTEM Filed Sept. 5, 1970 2 Sheets-Sheet E 'United States Patent 3,702,154 CONTINUOUS CASTING MACHINE RECIPROCA- TION AND WITHDRAWAL CONTROL SYSTEM Joseph Rokop and Geoffrey W. Hughes, Bethel Park, Pa., assignors to Pennsylvania Engineering Corporation Filed Sept. 3, 1970, Ser. No. 69,361 Int. Cl. B22d 11/12, 17/32 U.S. Cl. 164-154 9 Claims ABSTRACT OF THE DISCLOSURE A continuous casting machine having a flow through mold, hydraulically driven withdrawal rollers for withdrawing a molded strand from the mold, and hydraulically tion parallel with that of strand withdrawal to insure separation of the `strand therefrom during withdrawal. The Withdrawal speed is selectively adjustable to correspond to the metal pouring rate and control means effects simultaneous changes in the speed of the oscillating mechanism according to a preselected proportionally constant.

BACKGROUND lOF THE INVENTION This invention relates to continuous casting machinery and more particularly to means for controlling the speed of strand withdrawal and mold oscillation.

Continuous casting machines generally include a flow through type mold which receives molten metal through its open intake end and shapes the same into the desired crosssectional configuration. Prior to the initiation of a casting operation, the discharge end of the mold is plugged with a head member attached to an elongate starting bar or chain, the other end of which is engaged by the withdrawal mechanism. The molten metal is transported to the casting machine from a melting furnace by means of a ladle from which it is discharged into a tundish or molten metal transfer vessel disposed above the mold and having a discharge opening in its lower end positioned above the mold intake opening. After the molten metal had solidiiied around the head member, the latter is withdrawn from the mold by the withdrawal mechanism by acting through the agency of the starting bar. As the head member emerges from hte mold, it is followed by a continuously formed strand of metal which consists of an outer skin of solidified metal which encloses a molten core. The flow of molten metal into the mold from the tundish should be compensated by a corresponding withdrawal of solidified metal from the discharge end of the mold. The pouring rate may not remain uniform, however, since the molten metal tends to freeze around the tundish opening. If strand Withdrawal is too slow, the molten metal in the mold will overow onto the casting machinery which could result in damage or costly clean-up operations. On the other hand, if withdrawal of the strand is too rapid, the skin of solidified metal will not be sufiiciently thick whereby strand breakout is likely. It is accordingly necessary to co-ordinate the rate of strand withdrawal with the rate of metal solidification and feed rate of molten metal from the tundish.

The solidifying metal is separated from the mold by oscillating the latter rapidly in an axial direction. In order to prevent cracking, it is necessary that the separation occur when the mold is moving in the same direction as the strand and for this reason, the mold must move more rapidly than the strand is being withdrawn by the withdrawal mechanism. For this reason, prior art casting machines set the oscillation rate at a value which was higher than the fastest expected withdrawal speed. This was not wholly satisfactory, however, because as the tundish opening decreases to reduce the pouring rate, the withdrawal rate must be reduced accordingly to increase the 3,702,154 Patented Nov. 7, 1972 differences between oscillation and withdrawal rates which tends to cause undesirable skin effects on the strand.

An object of the invention is to provide a new and improved speed control means Afor the strand withdrawal and mold oscillating mechanisms of a continuous casting machine.

A further object of the invention is to provide a continuous casting machine wherein strand withdrawal and mold oscillating speeds are co-ordinated.

Yet another object of the invention is to provide control means for simultaneously adjusting strand withdrawal and mold oscillating speeds in accordance with a predetermined relation.

These and other objects and advantages of the instant invention will become apparent from the detailed description taken thereof with the accompanying drawings.

SUMMARY OF THE INVENTION In a continuous casting apparat-us having a mold for receiving molten metal, withdrawal means for Withdrawing at least partially solidified metal in a continuous strand from an opening in said mold and oscillating means for oscillating the mold to prevent the solidified metal from sticking thereto. First selectively operable control means for controlling the speed of strand withdrawal, second control means for controlling the speed of mold oscillation and adjustment means coupled to each control means for simultaneously adjusting each in a common sense and a predetermined relation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a side elevational view schematically illustrating a continuous casting machine incorporating the present invention;

FIG. 2 illustrates the strand withdrawal mechanism of FIG. l in greater detail;

FIG. 3 illusrates the mold oscillating mechanism of FIG. 1 in greater detail;

FIG. 4 is a schematic diagram illustrating the control mechanism according to the present invention; and

'FIG. 5 is a fragmentary view taken along lines 5--5 of FIG. 4.

DESCRIPTION 0F THE PREFERRED EMBODIMENT fully hereinbelow. In addition, a tundish or molten metal.

transfer vessel 15 is disposed above the mold 11 for receiving molten metal from a ladle 17 and for discharging the same into the mold 11. An open ended spray chamber 18 may be mounted below and in axial alignment with the mold 11 and may include a plurality of nozzles (not shown) for spraying the strand of molten metal as it discharges from the lower end of the mold 11.

Normally, the metal strand has a relatively thin skin of solidified metal as it discharges from the mold 11 and the spray chamber causes the metal to solidify at a faster rate to form a relatively heavier skin prior to passage of the strand to a roller apron 20 positioned below the spray chamber 18. The roller apron 20 consists of a pair of spaced channel members 21 and 22 for supporting a plurality of spaced apart and staggered rollers 24 which define the curvillnear path for the strand being cast as it emerges vertically from the spray chamber 1-8 and enters horizontally into the withdrawal mechanism 25.

come to rest. Similarly when switch 107 is placed in contact 112, a solenoid 99 will be energized to move valve element 97 to the left and thereby couple pump 103 to the upper end of cylinder 92. This will cause the piston 93 to move downwardly until solenoid 99 is deenergized and the valve element 97 returned to its neutral position whereupon piston 93 will again come to rest.

The lever assembly 88 includes a pair of levers 120 and 121 which are respectively pivotally connected to intermediate their ends to dixed fulcrums 123 and 124. The proximate ends of levers 120 and 121 are formed with registrable opposed notches 126 between which the stem 94 is received for being pivotally coupled by means of a longitudinal slot 127 formed in each lever and a pin 130 extending through the end of stem 94 and each of the slots 127. The remote ends of. the levers 120` and 121 are respectively coupled to threaded pump adjustment rods 132 and 133 by means of adjusting nuts 134 which are received in elongate slots 135 formed transversely through each of said levers. In addition, each of the pump adjusting rods 132 and 133 extends upwardly through openings 137 in each remote lever end and normal to the slots 135.

The pumps 89 and 90 may be of any well known type which are coupled for rotation at a constant speed by a shaft 138 to a constant speed motor 139 and whose outputs can be varied in accordance with longitudinal movement of an adjustment stem 140. One example of such a pump is the Vickers Variable Displacement Pump, Model PVB20. Each of the adjustment stems 140 is pinned to the end of one of the pump adjusting rods 132 or 133 whereby axial movement of either rod will modify the delivery of its respective pump.

The withdrawal roller assembly control 82 includes a irst'four-way solenoid operated valve 145 and a second double solenoid operated four-way valve 14'6. The valve 145 is normally held in its position shown in FIG. 4 by a spring 148 so that the pump 89 output conduit 149 is coupled to the input conduit 150 of a valve 146, and the motor return conduits 152 and 153 are coupled to conduit 155 which is connected to sump 104. When switch 156 is closed to complete an energizing circuit to solenoid 157, valve 145 is moved to an alternate position shown by the phantom lines in FIG. 4, wherein the motor return conduits 152 and 153 are coupled to pump 89 output conduit 149 and the valve 146 input conduit 150 is coupled to sump conduit 155.

Valve 146 includes a housing 160 and a reciprocating valve element 161 coupled for axial movement by solenoid 162 and 1'64 which are controlled by a switch 165. When switch 165 is on its neutral terminal 166, each of the solenoids 162 and 163 are deenergized and the element 161 will be held in its position shown in FIG. 4 by springs 1'67 and 168. In this position, the motor input conduits 169 and 170 are each coupled by valve element 161 to the valve 146 input conduit 150. When switch 165 is moved to terminal 172, to energize solenoid 163, the valve element 161 will move toward the right as viewed in FIG. 4 to uncouple the input conduits to motors 45a, and 46a from valve 146 input conduit 150, but as the result of the configuration of housing 160, the input conduit 170 to motors 47a and 48a will remain connected to conduit 150. On the other hand, when switch 165 is moved to contact 175 to energize solenoid 162, the valve element 161 will be moved toward the left to disconnect motors 47a and 48a from conduit 150 while motors 45a and 46a will remain connected thereto.

Referring now to oscillation motor 30, its input is shown to be coupled by conduit 177 to the pump 90 output. The motor 30 return is coupled to the sump 104 by a conduit 178 and counterbalance valve 180. The latter valve imposes a back pressure on the motor 30 output which balances the pressure caused by the weight of the mold 11. Thus, the mold 11 is prevented from moving downward- 1y as a result of its own weight but must be driven by motor 30 so as to overcome the counterbalancing effect of valve 180. If the mold 11 were free to move downwardly under its own weight, its speed in that direction could not be controlled. Valve 180 places a back pressure on the motor 30 which is greater than that produced by the mold 11 so that valve 80 will not open unless a pressure is delivered by the output of motor 30` which is greater than that resulting from the weight of the mold 11 alone.

The system is protected by pressure relief valves 182 and 183 which are operative to shunt the withdrawal motors 45a, 46a, 47a and 48a or the oscillation motor 30, respectively, in the event of an over pressure in the system. Each of the pressure relief valves 182 and 183 are shunted by solenoid operated valves 184 and 185 respectively so that the pressure relief valves can be by-passed when the respective hydraulic motors are at rest but the pumps 89 and 90 are operating.

In operation, the operator determines the desired relative rates of speed of withdrawal mechanism 25 and the oscillation motor 30 in accordance with the casting speed and pouring rate so that the molten metal in the mold will be maintained at approximately an optimum height. The motor speeds may be adjusted initially by means of nuts 134 which are turned to position stems 140 such that the outputs of pumps 89 and v90 are at an optimum value when the piston 93 is centered. This adjustment will preferably set the oscillation motor 30 at a speed which is approximately 10% faster than the withdrawal rate of motors 45a, 46a, 47a, and 48a. This insures optimum strand skin conditions.

It will be recalled that initially, the starting chain 61 will be disposed in the storage assembly `68. To commence the operation, the operator stationed at control console 190 releases the hydraulic mechanism 74 so that the end of the starting chain will move into a position between the exit roll assemblies 47 and 48 which are then clamped. The operator then closes switch 156 and moves switch 165 to contact 172. This couples the return conduit 153 of exit roller motors 47a and 48a to the pump 89 output conduit 149 and disconnects entrance roller motors 45a and 46a from the system. The exit rolls 47b and 48b will be driven in the reverse direction to move the starter chain I61 toward the entrance rolls 45b and 46b. When the latter rolls have engaged chain '61, switch 165 is moved to contact 166 whereby entry roller motors 45a and 46a will also be coupled to the pump 89 through conduits 149 and 152 for reverse operation so that the starting chain will be driven up roller apron 20 and toward the mold 11.

When the starting member 60 is disposed in a position to plug the lower end of the mold 11, the solenoid valve 184 is opened to shunt the system whereby the withdrawal assembly 25 comes to rest. The metal pouring operation may then commence with the opening of a valve 190 on the lower end of ladle 17 (FIG. l). As the molten metal Within the mold 11 begins to rise and solidify, the operator opens switch 156 to return valve 145 to its forward position relative to motors 45a, 46a, 47a and 48a as shown by full lines in FIG. 4. Solenoid valves 184 and 185 are then opened to couple pumps 8'9 and 90 to drive their respective motors. The withdrawal assembly 25 will then begin withdrawing the starting member 60 out of the end of the mold 11 followed by the strand being formed as the motor 30 oscillates the mold 11 to prevent sticking.

In the event that withdrawal is too rapid, whereby the level of molten metal in the mold 11 begins to recede to an undesirably low level, the operator will move switch 107 to contact 112 thereby energizing solenoid 99 to move valve element 97 toward the left as 'viewed in FIG. 4. This couples the upper end of cylinder 92 to pump 103 whereby the piston will be moved downwardly as the stem 94 depresses the approximate ends of levers 120 and 121. This, in turn, moves the control rods 140 of each of the pumps 89 and 90 outwardly to proportionately decrease the output of each of the pumps 89 and 90 so that the rate of withdrawal and the rate of oscillation of the mold 11 will decrease accordingly. As the result, the relative speeds of the strand and the mold 11 during oscillation will remai-n relatively constant. When the operator observes that the level of molten metal has returned to the desired level, he will move switch 107 to neutral Contact 110 so that the valve 97 will return to its central position wherein pump 103 will be vented to the sump 104 and the piston 93 will come to rest. The withdralwal roller and oscillating speeds will then remain constant at the new level.

Similarly, should the operator note that the level of molten metal in mold 11 begins rising above a desired level, indicating the necessity for more rapid withdrawal, the switch 107 will be moved to contact 111. This energizes solenoid 100 to move valve.` element 97 toward the right as viewed in FIG. 4 whereupon the lower end of the cylinder 92 will be connected to the pump 103. This `piston 93 will then begin rising to move the control rods 140 toward their respective pumps 89 and 90 substantially uniformly whereby more rapid pump delivery will be achieved. The withdrawal mechanism and oscillation motors will then begin operating more rapidly at the new withdralwal and oscillating speeds although the relative strand and mold speeds will remain relatively constant.

When the operation is terminated and the end of the strand being cast moves past the entrance roller asemblies 4.5 and 46 whereby it is necessary to disconnect the latter assemblies` so that power will remain on the exit roller assemblies 47 and 48, the switch 165 is moved onto contact 172 to move the valve element 161 toward the right as viewed in'FIG. 4 to disconnect the entry roller motors 45a and 46a from pump 89. The exit roller assemblies 47 and 48 continue to drive the chain 61 to its stored position and oscillation of the roller and oscillation motors is terminated.

rIn this manner, the withdra'wal and oscillating speeds can be controlled to conform tomold pouring rates while maintaining their speed relation at a desired value to insure optimum strand skin conditions. While the invention has been described in relation to a particular continuous casting apparatus, those skilled in the art will appreciate that it may be employed with other types of continuous casting apparatus. In addition, while particular hydraulic systems and components are illustrated in relation to the preferred embodiment of the invention, other systems and components capable of perform.- ing equivalent or analogous functions may also be employed. For example, functionally equivalent electrical components may be employed to provide an analogous electrical system. Accordingly, while only a single embodiment of the invention has been shown and described, it is not intended to be limited thereby, but only by the scope of the appended claims.

We claim:

1. In a continuous casting apparatus, including a mold in which molten metallat least partially solidifies to form a strand means,

said mold having a first opening lfor receiving molten metal and a second opening for discharging said strand means,

Withdrawal roller means engaging said stra-nd means for withdrawing the same in a first direction outwardly of said second opening,

first drive means coupled to said roller means for driving the same to effect withdrawal of said strand means,

oscillating means coupled to said mold for reciprocally moving said mold in said first direction and in an opposite direction to prevent said-strand means from adhering thereto, and including second drive means independent of said first drive means,

first adjustable control means coupled to said first drive means for controlling the withdrawal speed of said strand means Iwhereby the level of molten metal Within said mold may be maintained within desired limits,

second adjustable control means coupled to said second drive for controlling the speed of mold movement in said first direction,

said first a-nd second control means being initially adjusted and arranged to move said mold in said first direction at a predetermined faster rate than that of said strand means,

adjustment means selectively operable in a first and second sense,

and proportioning means coupled to said adjustment means and to said first control means for adjusting the speed of the strand means withdrawal in response to the operation of said adjustment means and in the same sense to control Athe level of molten metal in said mold, said proportioning means also being coupled to said second control means for simultaneously and proportionately adjusting the speed of mold movement in said first direction,

said proportioning means beingv constructed and arranged to adjust the mold speed in the same sense and relation as that of said strand means to maintain a substantially constant speed ratio between said mold and strand means,

said proportioning means including first and second adjustabley coupling means for respectively connecting the adjustment means to said first and second control means, each of such coupling means being simultaneously operable in the same sense by said adjustment means.

2. The apparatus set forth in claim 1 wherein said roller means -includes at least two pair of reversible rollers, the rollers of each pair engaging the opposite sides of said strand means, and third control means for selectively or jointly coupling or uncoupliug said pairs of rollers to said drive means independently of said proportioning means for selectively or jointly driving said pairs of rollers in a forward or reverse direction or for uncoupliug the same.

3. The apparatus set forth in claim 2 wherein the first and second drive means each includes variable output pump means, the rst and second control means each being Ioperable to vary the output of its respective pump means.

4. The apparatus set forth in claim 3 wherein said withdrawal rollers each include hydraulic motor means, said third control means including valve means.

5. The apparatus set forth in claim 1 wherein said first and second coupling means -are respectively adjustably connected to its respective control means to establish an initial operating speed relation between said mold and said withdrawal rolls and for corresponding increasing and decreasing the speed of each in accordance 'with said relation.

6. The apparatus set forth in claim 5 lwherein coupling means include first and second linkage means, each linkage means being coupled to said adjustment means and to said first and second control means for simultaneously adjusting each control in a common sense and in accordance with said speed relation.

7. The apparatus set forth in claim 6 wherein each of said linkage means includes a link pivotally mounted intermediate its ends and each coupled on one side of its respective pivot to said adjustment means and each being adjustably coupled on the other side thereof to its respective control means.

8. The apparatus set forth in claim 7 wherein said adjustment means includes a hydraulic cylinder and piston coupled to each of said link means on one side of their respective pivots, and valve means selectively operable for moving said piston in opposite directions within said cylinder.

9. The apparatus set forth in claim 8 wherein said first drive means includes at least two pair of reversible hydraulic roller means, said first and second drive means comprising variable output pump means, and valve means for selectively coupling and uncoupling said pairs of hydraulic roller means to said rst drive means independently of said proportioning means for driving said roller means in a forward or reverse direction or for selectively uncoupling the same.

References Cite'd UNITED STATES PATENTS 2,135,183 11/1938 Junghans 164-83 2,815,551 12/1957 Hessenberg et al. 164-83 2,818,616 1/195'8 Rossi 164--260 l0 6/1962 Haussner et al 164-154 10/1967 Rys 164-154 X 2/1969 Cruger et al 164-274 11/1970 Lemfer et al. 164-83 X 2/1971 Vertesi 164-154 X FOREIGN PATENTS 6/ 1960 Great Britain 164-282 U.S. Cl. X.R.

,Patent No, 3, 702,154 Dated November 7, 1972 Inventor(s) Joseph' Rokop and Geoffrey W. Hughes It is certified that error appears inthe above-identified patent and that said Letters Patent are hereby corrected as shown below:

in the drawings, Sheet 1, Figure 5, reference numeral 128 should read 127. In the drawings, Sheet 1, Figure 2, the hydraulic motor attached to roller assembly 47 should be labeled 47a; numeral 45a should read 45; the hydraulic motor attached then to roller assembly 45 should be labeled 45a; the drive roll of roller assembly 45 should be labeled 45b; the hydraulic motor attached to roller assembly 46 should be labeled 46a; the support frame of roller assemblies 46 and 48, located in the center of the drawing and shaped like an inverted U, should be labeled 50; the right pivot armvbetween frame 50 and roller assembly 45 should be labeled 51; and the piston at the left side of the figure should be labeled 53 instead of 55. inv the drawings, Sheet 2, Figure 4, the numeral 80 should be placed at the upper left of the drawings between the numerals 99 and 87 with an accompanying arrow pointing to the entire figure; the power source at the top l center of the figure should be labeled 108; the numeral .128 should read 127; the numeral 83 should be inserted generally in the area between the numerals 18.3, 11 and 30; the numeral 153 should be applied to the pipe leaving valve 145 to the right; andthe numeral 150 should be applied to the pipe leaving valve-145 to the left. At column 3, line 26, the numeral H44H should read 46-.

Signed and sealed this 3rd day of April 1973.

' (SEAL) Attest:

EDWARD l\/l.FLETSHER,JR. ROBERT GOTTSCHALK Attesting Off1cer- Commissioner of Patents FORM PO-1050 (1069) uscoMM-oc ooms-ps9 9 U.$. GOVERNMENT PRINIING OFFICE: i989 CI3SG-3IL 

